Prolific actor Lee Sun-kyun said the experience of working with rookie director Jason Yu on the soon-to-release “Sleep” gave him the opportunity to just focus on acting, with no need to concern himself with unnecessary things.

“After a long interval, ‘Sleep’ was a project that allowed me to just focus on acting, liberated from concerns about characters or being sidetracked by other things like changes in the plot (thanks to the director’s preparedness),” Lee told The Korea Herald in an interview in Seoul on Thursday.

In the mystery thriller “Sleep,” Yu’s full-length feature film debut, Lee plays newlywed Hyun-soo, who exhibits strange behavior while sleeping. His pregnant wife Soo-jin (Jung Yu-mi) tries to stop him in some way or other.

The film was invited to the noncompetitive Critics Week’s section at the 76th Cannes Film Festival in May.

“I suggested Yu to go for as many takes as he wanted so that he leaves no room for regrets when he sees the edited version. I also told him that he doesn’t need to stick to the storyboard all the time, which a rookie director would usually do,” said Lee. "But because the scenario and the storyboard were all already so succinct and straightforward, we were able to shoot more effectively.”

Yu, a former assistant to auteur Bong Joon-ho for 2017’s “Okja,” reignited Lee’s passion with fresh acting challenges. For example, Lee’s character eats raw meat, fish and uncooked egg straight from the refrigerator as part of his sleep disorder in the middle of the night -- a new experience for an actor with a career spanning almost two decades.

“I liked how I could try out new things in this film. Director Yu planned out all the procedures required for that scene, with staff even sending me a video of trial and error with a variety of raw foods. The staff prepared all food props in a hygienic way,” Lee said, adding that his experience of watching veteran actor Ahn Sung-ki eating a raw chicken leg in 1984’s “Whale Hunting” inspired him for “Sleep.”

“Thanks to director Yu’s detailed setting and considerate preparation, we only took five to six takes in that scene,” Lee said, adding that he actually wanted to shoot the scene several more times.

Lee shared that he decided to star in the rookie director's film partly because of a phone call from Yu’s mentor, Oscar-winning director Bong Joon-ho. Lee and Bong worked together on Cannes-winning “Parasite” in 2019.

“There is a widespread stereotype of rookie directors in our industry, such as distrust, but director Bong called me to reassure me about director Yu. And it turned out that he was a very talented, well-prepared, aspiring director,” said Lee.

In May, Lee visited Cannes with not one, but two films -- “Sleep” and “Project Silence” -- a rare and privileged experience for an actor. He was accompanied by his family – wife and actor Jeon Hye-jin and two sons -- for the first time despite several trips to Cannes before.

“It was really nice watching the film and doing the whole Cannes experience as a family. My two sons will never forget that experience, which I did for the first time and maybe the last time,” he added.

The 48-year-old actor’s thirst for performing won’t cease anytime soon.

“Because I’m an actor, I’m more used to successfully achieving acting when the role is given, instead of choosing what to do. But if I have an opportunity, I want to try superhero flicks, which I’ve recently been into,” he said.

“Acting is what powers me to grow and contemplate. I’m thankful that I’m doing this for a living,” Lee added.

“Sleep” hits local theaters on Sept. 6.